For many years asbestos has been used to impart texture, strength, and thixotropic properties to asphalt compositions. However, because indications are that asbestos is both toxic and carcinogenic many such products have fallen out of favor.
The search for improved cold-applied asphalt compositions where the asbestos used may be minimized or replaced entirely without a decrease in performance has been an on-going concern in the art. In conjunction with a non-asbestos fiber, asbestos may be replaced by a gelling clay, either alone or with a surfactant, to gel and thicken the asphalt. The use of surfactant however, introduces additional costs.
Many of these formulations have associated with them a number of significant problems and deficiencies. Most are related to inefficient formulation procedures and inadequate compositions performance, and result from the asphalt, filler, and other components currently used. Basically, required product viscosity is difficult to achieve initially and control because it "drifts" with time, and varies due to the fact that characteristics of raw materials change from load to load. Thus, excessive manufacturing time and unacceptable deviation from an acceptable norm on the finished product is encountered.